Little Miss Muffet Sat in the Lab: The Potential Applications of Spider Silk

Background:

What has eight legs and eight eyes? The monster in your nightmares? Although spiders are feared by many, nobody can deny that these creatures are capable of incredible feats of nature, one being their ability to spin silk.

Researchers from both China and the U.S. are currently using the silk created by the Ornithoctonus Huwena spider as inspiration for the creation of new materials and as well as the development of artificial muscle technology since spider silk and muscle fibres behave in similarly; particularly in the way that they are able to stretch and shrink based on changes within their environment.

figure
(a) A picture of the spider Ornithoctonus Huwena (b) photo of the spider webs that were collected by a piece of cardboard (c) a bundle of individual silk fibers (d) a close-up of the silk fiber and (f) is a “stress-strain curve”

Professor Hongwei Zhu of Tsinghua University’s School of Material Science and Engineering in Beijing, one of the researchers working on this project, describes spider silk as “a natural biological material with [a] high sensitivity to water” and so the silk’s sensitivity to water contributes to all the buzz. First, Zhu and his group of researchers examined the way in which silk fibres were actuated by water – this just means the flexing action that is activated by water- and then they put the spider silk to the test. Using electron microscopy, they were able to view the smooth threads that made up the silk and to get an even better look, they used a technique called Raman spectroscopy, which involves analysing the way light bounces off an object to determine what it is composed of. This method also allows researchers to examine what the object is made up of without actually dissecting the object. They were able to observe the exact protein structure that formed the fibres and explained that the stretching and shrinking action caused by water is because the protein molecules have a strong attraction to water and will change its shape when water is present.

To go a little more in depth, we must look at the structure of the proteins; more specifically the secondary protein structure which involves alpha-helices and beta pleated sheets. Alpha-helices are polypeptide chains (which are chains of many amino acids) that are arranged in a spiral structure. The researchers hypothesize that this structure attributes to how a silk protein can stretch and lengthen. This would be similar to a curled party ribbon in real life and how you can straighten and lengthen it out.

Beta pleated sheets are formed by the intermolecular attractions (attractive bonds existing between molecules) between strands of polypeptides to form something that looks similar to a pleated sheet (or an accordion fold with paper). This structure is thought to contribute to the strength of the silk which allows it to lift and dangle objects.

File:Alpha beta structure (2).png
On the left is the beta pleated sheet and on the right is the alpha helix structure. 

They also looked at how the proteins performed in weightlifting. First, they looked at the actuated state of the fibres while they were laying flat and then when it was attached and hanging from a fixed point. Then they threw in the weights and played a little Eye of the Tiger. The results did not disappoint. The spider silk could lift the weights very quickly and efficiently and over a long distance as well.

figure
A picture of the silk weight lifting

This test alone incites new approaches to our current technology and will allow us to expand the functionalities of our machines and devices. But the benefits do not stop there. There is an added positive of the sustainability factor of technology. Spider silk can be relaxed simply through the process of removing the water. Additionally, the water can be reused.

Zhu also comments that “this has provided the possibility that the spider silk can act as biomimetic muscle to fetch something with low energy cost. It can be further improved to complete staged shrink-stretch behaviour by designing the silk fiber’s thickness and controlling droplet’s volume.” Further uses of the spider silk would be in more flexible sensor devices.

What do I think?

Personally, I have a bad fear of spiders. The fear is not crippling, but spiders have the power to compel me to leave the room screaming. Nonetheless, reading about spiders and the application of the strings that come out of their bum area is fascinating and exciting. Instead of the metallic, high-tech view vision of our future, I quite enjoy the idea that we would be incorporating biological compounds in the technology we use because that keeps the human population grounded and closer to nature. If we develop better relationships and a dependency on animals and the ecosystem, then this will force us to preserve nature. Additionally, just the designs and plans that will be created on how this technology would look would be a fascinating thing that I am sure would earn its own exhibit at a museum.

I think the most interesting idea that I have taken away from this article is that spider silk is so similar to the way human muscle behaves. Although the spider silk is not connected to a brain, I strongly believe that the technology that people will create will act as a replacement to the brain, allowing the silk to be controlled in such a precise way, even humans cannot outperform it. And here is what I like the most. If this spider silk is so much like the human muscle, then it seems that it would be a pretty good substance that can be combined with technology to create a realistic bionic arm or other parts of the body. Even though the development process and the actual technology would be very complex and the cost may be high, someone who has lost one of their arms still has the possibility of gaining back at least partial functionality of having both arms.

Another great thing about this is how it is sustainable and reusable and the process is very simple too. It would not require the work of an entire factory just to be able to reuse the device. It does not seem as if many people are working avidly towards saving the Earth so if everybody can unintentionally do their part, we will be working towards a better Earth. By that, I just mean that although the spider silk is not sucking the smog out of the air, at least it is somewhat environmentally friendly. I just wonder if salt water will activate it.

Now, I cannot imagine what the researchers have in mind for this project but based on what Hongwei Zhu said about fetching items, I feel like it may be involved in many construction or retrieval projects. At the same time, I am sure that toy companies or the people who brought to you hover boards or drones would create a spider-man web-slinging device for personal use in-home so that you can grab things from across the room. (Maybe the first little snippet of this video will give what I am saying some context. This is what I was visualizing when I was writing that. And the look on his face when he gets his web shooter to work is so relatable when you finally succeed in something that frustrated you for hours. You can stop the video around 1:35.)

One thing that I am thinking about is how it could be used as a space arm like the Canadarm

The Canadarm – a robotic arm that helped the spaceship with its duties (e.g repairing satellites)

(Read more about Canadarm here: http://www.thecanadianencyclopedia.ca/en/article/canadarm/ ) or just a regular robot arm but I am just brainstorming here. Still, this begs the question of whether or not spider silk will work in space and other environments. Will humid or cold environments have any effect on the functionality of these technologies?

Some questions that I have with this concept right now are that spider silk is a biological compound and it is made from proteins. Even after some of the challenges that will be overcome, such as reaction to heat or other environmental factors, proteins and all biological matter are going to wear down and deteriorate. Will they be creating a synthetic material to be combined with the spider silk? Also, how long could natural spider silk last? If it is extremely durable, then it could be fashioned into ropes and cords too.

Another question I have is about the use of spiders. The spiders that they will be using can be artificially bred, but how are they going to squeeze enough web out of them for their projects. Will they have to create a material that is spider silk-like or will this turn into an ethical issue like the slaughtering of animals in the meat industry. Also, I do not know what the spider’s life span is but are we going to create a mass of spiders? That is on its way to horror movie-ville.

Also, non-venomous spiders do not deserve all the hate that they receive. They play an integral part of the animal and insect food chain, being the predators to certain critters (which is great because I also have a small fear of insects; the enemy of my enemy is my friend right?) And I think that the way that their bodies are built is pretty complex and efficient also. Even the geometry present in their webs is a wonder in itself (is a spider better at math than me?) They can scale up walls and stick to the ceiling and when they get tired of that, they can just drop an end of a web and climb down like a spy.

Anyway, this article also got me researching about Raman spectroscopy. I think that it is amazing how people can find such creative ways to solve problems like using photons!

Here is a great video I found that explained what it is:

Ok, I am also curious if this is true for all spider silk and if I can actuate spider silk at home? It is certainly a project I am thinking about. My neighbours have a lot of spider webs in their trees…

To read the article yourself: https://www.sciencedaily.com/releases/2017/01/170131104427.htm

To read the lab report published in the Applied Physics Letters: http://aip.scitation.org/doi/full/10.1063/1.4974350

Reference list:

Spider silk demonstrates Spider man-like abilities. Science Daily [Internet]. 2017 [cited 26 Feb 2017]. Available from: http://www.sciencedaily.com/releases/2017/01/170131104427.htm

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